Solid electrolytic capacitors (e.g., tantalum or niobium capacitors) have been a major contributor to the miniaturization of electronic circuits and have made possible the application of such circuits in extreme environments. Tantalum capacitors, for example, are typically made by compressing tantalum powder into a pellet, sintering the pellet to form a porous body, and then subjecting it to anodization to form a continuous dielectric oxide film on the sintered body. The capacitance of the tantalum anode is a direct function of the specific surface area of the sintered powder. Greater specific surface area may be achieved, of course, by increasing the grams of powder per pellet, but cost considerations have dictated that development be focused on means to increase the specific surface area per gram of powder utilized. Because decreasing the particle size of the tantalum powder produces more specific surface area per unit of weight, effort has been extended into ways of making the tantalum particles smaller without introducing other adverse characteristics that often accompany size reduction.
One technique employed for increasing the specific surface area of tantalum powder involves flattening the powder particles into a flake shape. For example, U.S. Pat. No. 4,940,490 to Fife, et al. is directed to a flaked tantalum powder prepared by deforming or flattening a granular tantalum powder, followed by a size reduction step until a Scott density greater than about 18 g/in3 is achieved. Preferably, this size reduction process is aided by embrittling the flake by techniques such as hydriding, oxidizing, cooling to low temperatures, etc., to enhance breakage when reducing the flake particle size by mechanical means such as crushing, or other size reduction processes. Unfortunately, the technique of the '490 patent is relatively cost prohibitive and inefficient in that the powder is subjected to multiple complex processing steps before it may be used to form a capacitor anode.
As such, a need currently exists for a more efficient and cost effective technique of forming a capacitor anode from flake particles.